The invention is based on a device for generating bias voltage for a rotationally or linearly vibrating rotation rate sensor.
Rotation rate sensors that utilize the Coriolis effect are known in conjunction with systems in motor vehicles for controlling vehicle dynamics and are put on m the market by the present applicant in the form of micromechanical rotation rate sensors. A rotation rate sensor has one or more seismic masses, which by means of a voltage generated in an electronic circuit is excited to perform mechanical vibration. This vibration acts on one or more acceleration sensors, which upon a rotation of the system measure the Coriolis acceleration acting on the vibrating masses. From the excitation and acceleration signals,,the rotation rate of the system can be determined with the aid of an evaluation circuit.
An additional electrical test signal, which is fed to the acceleration sensor or sensors, can serve to cause an additional, arbitrarily generated acceleration to act on the sensor. Thus information about the properties of the acceleration sensor and the downstream evaluation circuit, for instance, can be obtained. It is accordingly also possible to detect errors, and in particular systematic errors. This is especially important, since rotation rate sensors that evaluate the Coriolis effect exhibit systematic errors, whose effects on the measurement signal must be minimized by a suitable choice of evaluation methods.
In German Patent Disclosure DE 199 10 415, a method and an apparatus for tuning a first oscillator with a second oscillator are described. Two frequency-and phase-shifted signals symmetrical to the vibration of the second oscillator are used to determine the response behavior of the first oscillator. As a function of the difference in response behaviors, tuning of the first oscillator with reference to the second oscillator is performed. For amplitude correction, a quotient is formed from the output signal and the sum of response behaviors. This method and the apparatus can be used in particular in. a rotation rate sensor. They assure that the evaluation conditions for the Coriolis force are stable. Temperature changes and aging effects can also be compensated for automatically; by means of the closed-loop control circuit, the vibrations of the two oscillators can be tuned to one another. The known method makes it no longer necessary to locate the detection mode as far away from the oscillator frequency as possible.
From German Patent Disclosure DE-A 196 53 021, a device for ascertaining a rotation rate with a rotation rate sensor is known, which among other things is a standard for the Coriolis acceleration and thus for the rotation rate as well. The output signals of the rotation rate sensor are pulse width modulated or sigma-xcex94 signals. These signals are delivered to a digital evaluation circuit, which has a subtractor, a multiplier, and a phase shifter. The phase shifter is supplied with the carrier signal, which excites the rotation rate sensor to vibrate; the digital phase shifter puts the carrier signal in phase with the Coriolis acceleration components, and the associated signal is delivered to the multiplier. The output signal of the multiplier is delivered, via a digital/analog converter and a low-pass filter, to the output, where the desired rotation rate signal is available.
The device according to the invention for generating bias voltage for a rotationally or linearly vibrating rotation rate sensor leads to the advantage that an appearance of a quadrature signal, which could adversely affect the ascertainment of the rotation rate signal, is avoided or at least minimized by a generation of suitable bias voltage signals for the electrode arrangement. On the basis of these bias voltage signals, electrostatic forces occur that act on the rotation rate sensor, which by way of example is constructed in the shape of a disk. By means of these forces, the rotation rate sensor is inclined in such a way that the quadrature signal is minimized. In order to incline the rotation rate sensor in a desired direction, it suffices to predetermine potential differences between the detection electrodes. This can be done by a predetermination of two output signals UQ1 and UQ2 from the quadrature compensator; these output signals affect the bias voltages fed to the electrodes. To compensate for the quadrature signal when the rotation rate sensor is in rotation, preferably four and in the case of a linear rotation rate sensor at least two electrodes, disposed below the sensor structure, are acted upon by suitable bias voltages.
Further advantages of the device of the invention reside in an improvement of the measurement resolution, andxe2x80x94since the quadrature component is suppressed adaptivelyxe2x80x94in the fact that aging and temperature dependencies and the necessity for calibration are avoided.